The induction of cyclooxygenase-1 by a tobacco carcinogen in U937 human macrophages is correlated to the activation of NF-kappaB

Dihydroartemisinin, a potential PTGS1 inhibitor, potentiated cisplatin-induced cell death in non-small cell lung cancer through activating ROS-mediated multiple signaling pathways

Dihydroartemisinin (DHA) exerts an anti-tumor effect in multiple cancers, however, the molecular mechanism of DHA and whether DHA facilitates the anti-tumor efficacy of cisplatin in non-small cell lung cancer (NSCLC) are unclear. Here, we found that DHA potentiated the anti-tumor effects of cisplatin in NSCLC cells by stimulating reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, C-Jun-amino-terminal kinase (JNK) and p38 MAPK signaling pathways both in vitro and in vivo. Of note, we demonstrated for the first time that DHA inhibits prostaglandin G/H synthase 1 (PTGS1) expression, resulting in enhanced ROS production. Importantly, silencing PTGS1 sensitized DHA-induced cell death by increasing ROS production and activating ER-stress, JNK and p38 MAPK signaling pathways. In summary, our findings provided new experimental basis and therapeutic prospect for the combined therapy with DHA and cisplatin in some NSCLC patients.

Vagus nerve stimulation as immunomodulatory therapy for stroke: A comprehensive review

Stroke is a devastating cerebrovascular pathology with high morbidity and mortality. Inflammation plays a central role in the pathophysiology of stroke. Vagus nerve stimulation (VNS) is a promising immunomodulatory method that has shown positive effects in stroke treatment, including neuroprotection, anti-apoptosis, anti-inflammation, antioxidation, reduced infarct volume, improved neurological scores, and promotion of M2 microglial polarization. In this review, we summarize the current knowledge about the vagus nerve's immunomodulatory effects through the cholinergic anti-inflammatory pathway (CAP) and provide a comprehensive assessment of the available experimental literature focusing on the use of VNS in stroke treatment.

Noxious Combination of Tobacco Smoke Nitrosamines with Bile, Deoxycholic Acid, Promotes Hypopharyngeal Squamous Cell Carcinoma, via NFκB, In Vivo

Tobacco smoking is the most known risk factor for hypopharyngeal cancer. Bile reflux has recently been documented as an independent risk factor for NFκB-mediated hypopharyngeal squamous cell carcinoma. However, the carcinogenic effect of tobacco smoke on the hypopharynx and its combination with bile has not yet been proven by direct evidence. We investigated whether in vivo chronic exposure (12-14 weeks) of murine (C57Bl/6J) hypopharyngeal epithelium to tobacco smoke components (TSC) [N-nitrosamines; 4-(N-Methyl-N-Nitrosamino)-1-(3-pyridyl)-1-butanone (0.2 mmol/L), N-nitrosodiethylamine (0.004 mmol/L)], as the sole drinking fluid 5 days per week, along with topically applied (two times/day) bile [deoxycholic acid (0.28 mmol/L)], can accelerate a possible TSC-induced neoplastic process, by enhancing NFκB activation and the associated oncogenic profile, using histologic, IHC, and qPCR analyses. We provide direct evidence of TSC-induced premalignant lesions, which can be exacerbated by the presence of bile, causing invasive carcinoma. The combined chronic exposure of the hypopharynx to TSC with bile causes advanced NFκB activation and profound overexpression of Il6, Tnf, Stat3, Egfr, Wnt5a, composing an aggressive phenotype. We document for the first time the noxious combination of bile with a known risk factor, such as tobacco smoke nitrosamines, in the development and progression of hypopharyngeal cancer, via NFκB, in vivo. The data presented here encourage further investigation into the incidence of upper aerodigestive tract cancers in smokers with bile reflux and the early identification of high-risk individuals in clinical practice. This in vivo model is also suitable for large-scale studies to reveal the nature of inflammatory-associated aerodigestive tract carcinogenesis and its targeted therapy.

PREVENTION RELEVANCE

Early assessment of bile components in refluxate of tobacco users can prevent the chronic silent progression of upper aerodigestive tract carcinogenesis. This in vivo model indicates that bile reflux might have an additive effect on the tobacco-smoke N-nitrosamines effect and could be suitable for large-scale studies of diagnostic and therapeutic interventions.

The role of macrophage polarization and function in environmental toxicant-induced cancers

Macrophages are a critical member of the innate immune system and can intensify tumor invasiveness and assist the growth of neoplastic cells. Moreover, they have the capability to reinforce immunosuppression and angiogenesis. Various investigations suggest that health-related issues, including inflammatory disorders and neoplastic diseases may be caused by environmental toxicant exposure. However, it is still unclear what role these environmental toxicants play in causing carcinogenesis by disturbing the mechanisms of migration, polarization, differentiation, and immune-stimulatory functions of macrophages. Accordingly, in this article, we will explore the interaction between environmental chemicals and inflammatory macrophage processes at the molecular level and their association with tumor progression and carcinogenesis.

Regulatory function of peroxiredoxin I on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung cancer development

Smoking is a major cause of lung cancer, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the most important carcinogens in cigarette smoke. NNK modulates the expression of peroxiredoxin (Prdx) I in lung cancer. Prdx1 is upregulated in lung squamous cell carcinoma and lung adenocarcinoma, and considered a potential biomarker for lung cancer. The current article reviewed the role and regulatory mechanisms of Prdx1 in NNK-induced lung cancer cells. Prdx1 protects erythrocytes and DNA from NNK-induced oxidative damage, prevents malignant transformation of cells and promotes cytotoxicity of natural killer cells, hence suppressing tumor formation. In addition, Prdx1 has the ability to prevent NNK-induced lung tumor metabolic activity and generation of large amount of reactive oxygen species (ROS) and ROS-induced apoptosis, thus promoting tumor cell survival. In contrast to this, Prdx1, together with NNK, can promote the epithelial-mesenchymal transition and migration of lung tumor cells. The signaling pathways associated with NNK and Prdx1 in lung cancer cells have been discussed in present review; however, numerous potential pathways are yet to be studied. To develop novel methods for treating NNK-induced lung cancer, and improve the survival rate of patients with lung cancer, further research is needed to understand the complete mechanism associated with NNK.

Carcinogenesis: Failure of resolution of inflammation?

Inflammation in the tumor microenvironment is a hallmark of cancer and is recognized as a key characteristic of carcinogens. However, the failure of resolution of inflammation in cancer is only recently being understood. Products of arachidonic acid and related fatty acid metabolism called eicosanoids, including prostaglandins, leukotrienes, lipoxins, and epoxyeicosanoids, critically regulate inflammation, as well as its resolution. The resolution of inflammation is now appreciated to be an active biochemical process regulated by endogenous specialized pro-resolving lipid autacoid mediators which combat infections and stimulate tissue repair/regeneration. Environmental and chemical human carcinogens, including aflatoxins, asbestos, nitrosamines, alcohol, and tobacco, induce tumor-promoting inflammation and can disrupt the resolution of inflammation contributing to a devastating global cancer burden. While mechanisms of carcinogenesis have focused on genotoxic activity to induce mutations, nongenotoxic mechanisms such as inflammation and oxidative stress promote genotoxicity, proliferation, and mutations. Moreover, carcinogens initiate oxidative stress to synergize with inflammation and DNA damage to fuel a vicious feedback loop of cell death, tissue damage, and carcinogenesis. In contrast, stimulation of resolution of inflammation may prevent carcinogenesis by clearance of cellular debris via macrophage phagocytosis and inhibition of an eicosanoid/cytokine storm of pro-inflammatory mediators. Controlling the host inflammatory response and its resolution in carcinogen-induced cancers will be critical to reducing carcinogen-induced morbidity and mortality. Here we review the recent evidence that stimulation of resolution of inflammation, including pro-resolution lipid mediators and soluble epoxide hydrolase inhibitors, may be a new chemopreventive approach to prevent carcinogen-induced cancer that should be evaluated in humans.

The Role of α7nAChR-Mediated Cholinergic Anti-inflammatory Pathway in Immune Cells

Alpha 7 nicotinic acetylcholine receptor (α7nAChR) is widely distributed in the nervous and non-cholinergic immune systems. It is necessary for the cholinergic transmitter to participate in the regulation of inflammatory response and is the key element of cholinergic anti-inflammatory pathway (CAP). Because of the profound impact of CAP on the immune system, α7nAChR is considered as a potential therapeutic target for the treatment of inflammatory diseases. Available evidences confirmed that manipulation of CAP by activating α7nAChR with either endogenous acetylcholine (ACh) or cholinergic agonists can substantially alleviate inflammatory responses both in vivo and in vitro. However, the mechanism through which CAP curbs the excessive pro-inflammatory responses and maintains immune homeostasis is not fully understood. Obtained clues suggest that the crosstalk between CAP and classical inflammatory pathways is the key to elucidate the anti-inflammatory mechanism, and the impacts of CAP activation in α7nAChR-expressing immune cells are the foundation of the immunoregulatory property. In this article, we review and update the knowledge concerning the progresses of α7nAChR-based CAP, including α7nAChR properties, signal transductions, interactions with classic immune pathways, and immunoregulatory functions in different immune cells. Certain critical issues to be addressed are also highlighted. By providing a panoramic view of α7nAChR, the summarized evidences will pave the way for the development of novel anti-inflammatory reagents and strategy and inspire further researches.

Mechanisms of Renal-Splenic Axis Involvement in Acute Kidney Injury Mediated by the α7nAChR-NF-κB Signaling Pathway

This study aimed to investigate the effect of splenectomy on dexmedetomidine-activated cholinergic anti-inflammatory pathway-mediated alleviation of LPS-induced AKI. A mouse model of septic kidney injury was established in C57BL/6 mice. A total of 30 C57BL/6 mice were randomly divided into the control group, LPS group, dexmedetomidine + LPS group, splenectomy group, splenectomy + LPS group, and splenectomy + dexmedetomidine + LPS group. The pathological effects in kidney tissues in each group were analyzed by HE staining. Apoptosis in each group was examined by the TUNEL method. Cr and Cys-C levels in each group were measured by ELISA. The expression levels of IL-6, NF-κB p65, Caspase-3, the antiapoptotic protein Bcl-2, the proapoptotic protein Bax, and α7nAChR in each group were measured by qRT-PCR and Western blotting. Dexmedetomidine alone reduced apoptosis in kidney tissue; however, apoptosis was increased after splenectomy in mice treated with dexmedetomidine. Splenectomy reduced the production of proinflammatory cytokines in circulation and had a protective effect on the kidney. Splenectomy inhibited dexmedetomidine-mediated activation of the α7nAChR pathway. Dexmedetomidine effectively alleviated LPS-induced kidney injury, and splenectomy inhibited the anti-inflammatory, antiapoptotic, and renoprotective effects of dexmedetomidine. The kidney-spleen axis is mediated by the α7nAChR-NF-κB signaling pathway and is involved in the development of AKI.

Tumor resistance mechanisms and their consequences on γδ T cell activation

Human γδ T lymphocytes are predominated by two major subsets, defined by the variable domain of the δ chain. Both, Vδ1 and Vδ2 T cells infiltrate in tumors and have been implicated in cancer immunosurveillance. Since the localization and distribution of tumor-infiltrating γδ T cell subsets and their impact on survival of cancer patients are not completely defined, this review summarizes the current knowledge about this issue. Different intrinsic tumor resistance mechanisms and immunosuppressive molecules of immune cells in the tumor microenvironment have been reported to negatively influence functional properties of γδ T cell subsets. Here, we focus on selected tumor resistance mechanisms including overexpression of cyclooxygenase (COX)-2 and indolamine-2,3-dioxygenase (IDO)-1/2, regulation by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL-R4 pathway and the release of galectins. These inhibitory mechanisms play important roles in the cross-talk of γδ T cell subsets and tumor cells, thereby influencing cytotoxicity or proliferation of γδ T cells and limiting a successful γδ T cell-based immunotherapy. Possible future directions of a combined therapy of adoptively transferred γδ T cells together with γδ-targeting bispecific T cell engagers and COX-2 or IDO-1/2 inhibitors or targeting sialoglycan-Siglec pathways will be discussed and considered as attractive therapeutic options to overcome the immunosuppressive tumor microenvironment.

TRAIL-Receptor 4 Modulates γδ T Cell-Cytotoxicity Toward Cancer Cells

Acquired immune evasion is one of the mechanisms that contributes to the dismal prognosis of cancer. Recently, we observed that different γδ T cell subsets as well as CD8⁺ αβ T cells infiltrate the pancreatic tissue. Interestingly, the abundance of γδ T cells was reported to have a positive prognostic impact on survival of cancer patients. Since γδ T cells utilize TNF-related apoptosis inducing ligand (TRAIL) for killing of tumor cells in addition to granzyme B and perforin, we investigated the role of the TRAIL-/TRAIL-R system in γδ T cell-cytotoxicity toward pancreatic ductal adenocarcinoma (PDAC) and other cancer cells. Coculture of the different cancer cells with γδ T cells resulted in a moderate lysis of tumor cells. The lysis of PDAC Colo357 cells was independent of TRAIL as it was not inhibited by the addition of neutralizing anti-TRAIL antibodies or TRAIL-R2-Fc fusion protein. In accordance, knockdown (KD) of death receptors TRAIL-R1 or TRAIL-R2 in Colo357 cells had no effect on γδ T cell-mediated cytotoxicity. However, KD of decoy receptor TRAIL-R4, which robustly enhanced TRAIL-induced apoptosis, interestingly, almost completely abolished the γδ T cell-mediated lysis of these tumor cells. This effect was associated with a reduced secretion of granzyme B by γδ T cells and enhanced PGE2 production as a result of increased expression level of synthetase cyclooxygenase (COX)-2 by TRAIL-R4-KD cells. In contrast, knockin of TRAIL-R4 decreased COX-2 expression. Importantly, reduced release of granzyme B by γδ T cells cocultured with TRAIL-R4-KD cells was partially reverted by bispecific antibody [HER2xCD3] and led in consequence to enhanced lysis of tumor cells. Likewise, inhibition of COX-1 and/or COX-2 partially enhanced γδ T cell-mediated lysis of TRAIL-R4-KD cells. The combination of bispecific antibody and COX-inhibitor completely restored the lysis of TRAIL-R4-KD cells by γδ T cells. In conclusion, we uncovered an unexpected novel role of TRAIL-R4 in tumor cells. In contrast to its known pro-tumoral, anti-apoptotic function, TRAIL-R4 augments the anti-tumoral cytotoxic activity of γδ T cells.

Intestinal Anti-Inflammatory Effect of a Peptide Derived from Gastrointestinal Digestion of Buffalo (Bubalus bubalis) Mozzarella Cheese

Under physiological conditions, the small intestine represents a barrier against harmful antigens and pathogens. Maintaining of the intestinal barrier depends largely on cell–cell interactions (adherent-junctions) and cell–matrix interactions (tight-junctions). Inflammatory bowel disease is characterized by chronic inflammation, which induces a destructuring of the architecture junctional epithelial proteins with consequent rupture of the intestinal barrier. Recently, a peptide identified by Bubalus bubalis milk-derived products (MBCP) has been able to reduce oxidative stress in intestinal epithelial cells and erythrocytes. Our aim was to evaluate the therapeutic potential of MBCP in inflammatory bowel disease (IBD). We studied the effect of MBCP on (i) inflamed human intestinal Caco2 cells and (ii) dinitrobenzene sulfonic acid (DNBS) mice model of colitis. We have shown that MBCP, at non-cytotoxic concentrations, both in vitro and in vivo induced the adherent epithelial junctions organization, modulated the nuclear factor (NF)-κB pathway and reduced the intestinal permeability. Furthermore, the MBCP reverted the atropine and tubocurarine injury effects on adherent-junctions. The data obtained showed that MBCP possesses anti-inflammatory effects both in vitro and in vivo. These results could have an important impact on the therapeutic potential of MBCP in helping to restore the intestinal epithelium integrity damaged by inflammation.

The effects of para-phenylenediamine (PPD) on the skin fibroblast cells

1. Para-phenylenediamine (PPD) is the commonest and most well-known component of hair dyes. PPD is found in more than 1000 hair dye formulations and is the most frequently used permanent hair dye component in Europe, North America and East Asia. PPD containing hair dyes have been associated with cancer and mutagenicity. Apart from that, PPD has potential toxicity which includes acute toxicity such as allergic contact dermatitis and subacute toxicity. 2. In this study, we examined the effects of the PPD composition on the skin-isolated fibroblast cells. Fibroblast cells were isolated from the skin and cell viability, reactive oxygen species (ROS) production, the collapse of mitochondrial membrane potential (MMP), lipid peroxidation (LPO), damage to the lysosome release of lactate dehydrogenase (LDH) and finally release of cytochrome c were examined following the exposure to various concentrations of PPD. 3. Our results showed that exposure to PPD increased ROS generation, LPO, the collapse of MMP, LDH release and cytochrome c release. Our results suggest that PPD can induce damage to the lysosomal membrane. 4. These results showed that PPD composition has a selective toxicity on skin fibroblasts cell and mitochondria are considered one of the goals of its toxicity.

The effect of environmental chemicals on the tumor microenvironment

Potentially carcinogenic compounds may cause cancer through direct DNA damage or through indirect cellular or physiological effects. To study possible carcinogens, the fields of endocrinology, genetics, epigenetics, medicine, environmental health, toxicology, pharmacology and oncology must be considered. Disruptive chemicals may also contribute to multiple stages of tumor development through effects on the tumor microenvironment. In turn, the tumor microenvironment consists of a complex interaction among blood vessels that feed the tumor, the extracellular matrix that provides structural and biochemical support, signaling molecules that send messages and soluble factors such as cytokines. The tumor microenvironment also consists of many host cellular effectors including multipotent stromal cells/mesenchymal stem cells, fibroblasts, endothelial cell precursors, antigen-presenting cells, lymphocytes and innate immune cells. Carcinogens can influence the tumor microenvironment through effects on epithelial cells, the most common origin of cancer, as well as on stromal cells, extracellular matrix components and immune cells. Here, we review how environmental exposures can perturb the tumor microenvironment. We suggest a role for disrupting chemicals such as nickel chloride, Bisphenol A, butyltins, methylmercury and paraquat as well as more traditional carcinogens, such as radiation, and pharmaceuticals, such as diabetes medications, in the disruption of the tumor microenvironment. Further studies interrogating the role of chemicals and their mixtures in dose-dependent effects on the tumor microenvironment could have important general mechanistic implications for the etiology and prevention of tumorigenesis.

Enhancement on reactive oxygen species and COX-1 mRNA levels modulate the vascular relaxation induced by sodium nitroprusside in denuded mice aorta

This study aimed to investigate the modulation of nitric oxide/reactive oxygen species in sodium nitroprusside relaxation in mice aorta. Sodium nitroprusside induced relaxation in endothelium-intact (e+) and endothelium-denuded (e-) aortas with greater potency in e+ than in e-. The nitric oxide synthase inhibitor did not alter the sodium nitroprusside relaxation in both e+ and e- aortas. However, the superoxide anion scavenger abolished the difference in sodium nitroprusside potency between e+ and e-. Sodium nitroprusside reduced dihydroethidium-derived fluorescent products in both groups; however, the difference between intact and denuded mice aorta remains. The glutathione levels and basal antioxidant activity of superoxide dismutase were reduced in e- aorta when compared with e+, and these values were not altered by sodium nitroprusside. Confirming these results, the levels of lipid peroxidation in e+ were significantly lower when compared to e-, and these values were not altered by sodium nitroprusside. The sodium nitroprusside potency in the presence of a nonselective COX inhibitor or the EP/DP prostaglandin receptor antagonist in endothelium denuded was similar to that in intact mice aorta. Based on these results, we performed the COX-1 and COX-2 mRNA level studies, and in denuded mice aorta, there was an upregulation in COX-1 mRNA levels. Taken together, our findings show that in the absence of endothelium, there is an enhancement of superoxide levels, leading to GSH consumption and higher levels of lipid peroxidation, showing an intense redox status. Furthermore, in denuded mice aorta, there was an upregulation of COX-1 mRNA expression, leading to vasoconstrictor prostanoids synthesis. The interaction of vasoconstrictor prostanoids with its receptors EP/DP negatively modulates the vascular relaxation induced by SNP in denuded mice aorta.

In vitro exposure of tobacco specific nitrosamines decreases the rat lung phospholipids by enhanced phospholipase A2 activity

Tobacco-specific nitrosamines (TSNA) have implications in the pathogenesis of various lung diseases and conditions are prevalent even in non-smokers. N-nitrosonornicotine (NNN) and 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are potent pulmonary carcinogens present in tobacco product and are mainly responsible for lung cancer. TSNA reacts with pulmonary surfactants, and alters the surfactant phospholipid. The present study was undertaken to investigate the in vitro exposure of rat lung tissue slices to NNK or NNN and to monitor the phospholipid alteration by [(32)P]orthophosphate labeling. Phospholipid content decreased significantly in the presence of either NNK or NNN with concentration and time dependent manner. Phosphatidylcholine (PC) is the main phospholipid of lung and significant reduction was observed in PC ∼61%, followed by phosphatidylglycerol (PG) with 100μM of NNK, whereas NNN treated tissues showed a reduction in phosphatidylserine (PS) ∼60% and PC at 250μM concentration. The phospholipase A2 assays and expression studies reveal that both compounds enhanced phospholipid hydrolysis, thereby reducing the phospholipid content. Collectively, our data demonstrated that both NNK and NNN significantly influenced the surfactant phospholipid level by enhanced phospholipase A2 activity.

Therapeutic Implications of Black Seed and Its Constituent Thymoquinone in the Prevention of Cancer through Inactivation and Activation of Molecular Pathways

The cancer is probably the most dreaded disease in both men and women and also major health problem worldwide. Despite its high prevalence, the exact molecular mechanisms of the development and progression are not fully understood. The current chemotherapy/radiotherapy regime used to treat cancer shows adverse side effect and may alter gene functions. Natural products are generally safe, effective, and less expensive substitutes of anticancer chemotherapeutics. Based on previous studies of their potential therapeutic uses, Nigella sativa and its constituents may be proved as good therapeutic options in the prevention of cancer. Black seeds are used as staple food in the Middle Eastern Countries for thousands of years and also in the treatment of diseases. Earlier studies have shown that N. sativa and its constituent thymoquinone (TQ) have important roles in the prevention and treatment of cancer by modulating cell signaling pathways. In this review, we summarize the role of N. sativa and its constituents TQ in the prevention of cancer through the activation or inactivation of molecular cell signaling pathways.

Cyclooxygenase-1 mediated platelet reactivity in young male smokers

BACKGROUND

The purpose of this study is to investigate the acute and chronic effects of cigarette smoking on cyclooxygenase- 1(COX-1)-mediated platelet reactivity among cigarette smokers.

METHODS

The levels of collagen-induced platelet aggregation, platelet COX-1 activity, and expressions were compared between smokers and age-matched nonsmokers. In smokers, the acute effects of cigarette smoking were assessed by repeating these measurements an hour after smoking.

RESULTS

Twenty-five smokers and age-matched nonsmokers (all men; mean age, 29 years) were studied. Collagen-induced platelet aggregation and plasma/urinary thromboxane B2 (TXB2) and 11-dehydroxythromboxane B2 levels were higher in cigarette smokers compared to nonsmokers. Greater expression of platelet COX-1 was observed in smokers than in nonsmokers. Among smokers, collagen-induced platelet aggregation correlated positively with platelet volume and circulating nicotine and cotinine concentrations. The levels of plasma/urinary TXB2 were significantly increased an hour after cigarette smoking.

CONCLUSION

Cigarette smoking aggravates COX-1-mediated platelet reactivity in young, otherwise healthy, smoking men.

Intracellular redox equilibrium is essential for the constitutive expression of AP-1 dependent genes in resting cells: studies on TGF-β1 regulation

The mechanisms involved in the continuous expression of constitutive genes are unclear. We hypothesize that steady state intracellular reactive oxygen species (ROS), which their levels are tightly maintained, could be regulating the expression of these constitutive genes in resting cells. We analyzed the regulation of an important constitutive gene, TGF-β1, after decreasing intracellular ROS concentration in human mesangial cells. Decreased intracellular hydrogen peroxide by catalase addition reduced TGF-β1 protein, mRNA expression and promoter activity. Furthermore, catalase decreased the basal activity of Activated Protein-1 (AP-1) that regulates TGF-β1 promoter activity. This effect disappeared when AP-1 binding site was removed. Similar results were observed with another protein containing AP-1 binding sites in its promoter, such as eNOS, but it was not the case in other constitutive genes without any AP-1 binding site, as COX1 or PKG1. The pharmacological inhibition of the different ROS synthesis sources by blocking NADPH oxidase, the mitochondrial respiratory chain or xanthine oxidase, or the use of human fibroblasts with genetically deficient mitochondrial activity, induced a similar, significant reduction of steady state ROS concentration as the one observed with catalase. Moreover, there was decreased TGF-β1 expression in all the cases excepting the xanthine oxidase blockade. These findings suggest a novel role for the steady state intracellular ROS concentration, where the compartmentalized, different systems involved in the intracellular ROS production, could be essential for the expression of constitutive AP1-dependent genes, as TGF-β1.

A possible ambivalent role for relaxin in human myometrial and decidual cells in vitro

PURPOSE

Based on the reported tocolytic action of the hormone relaxin (RLX) in rodents, locally produced in reproductive tissues and the corpus luteum in mammals, the present study aimed to evaluate the influence of RLX on contraction-mediating cyclooxygenases-1 and -2 (COX) and the contractile prostaglandin PGE(2) in human myometrial and decidual cells. Primary cultured cells were obtained from uteri and placentas of term and preterm women undergoing elective caesarean section.

METHODS

In vitro culture of primary myometrial and decidual cells, immunocytochemistry, reverse transcription and real-time PCR, Western blot, ELISA.

RESULTS

We demonstrate for the first time an activating effect of RLX for human COX-1 and COX-2 in primary myometrial and decidual cells in vitro.

CONCLUSIONS

These effects might potentially contribute to birth-associated induction of contractions in vivo.

Altered monocyte cyclo-oxygenase response in non-obese diabetic mice

Monocytes infiltrate islets in non-obese diabetic (NOD) mice. Activated monocyte/macrophages express cyclo-oxygenase-2 (COX-2) promoting prostaglandin-E(2) (PGE(2)) secretion, while COX-1 expression is constitutive. We investigated in female NOD mice: (i) natural history of monocyte COX expression basally and following lipopolysaccharide (LPS) stimulation; (ii) impact of COX-2 specific inhibitor (Vioxx) on PGE(2), insulitis and diabetes. CD11b(+) monocytes were analysed for COX mRNA expression from NOD (n = 48) and C57BL/6 control (n = 18) mice. NOD mice were treated with either Vioxx (total dose 80 mg/kg) (n = 29) or methylcellulose as control (n = 29) administered by gavage at 4 weeks until diabetes developed or age 30 weeks. In all groups, basal monocyte COX mRNA and PGE(2) secretion were normal, while following LPS, after 5 weeks of age monocyte/macrophage COX-1 mRNA decreased (P < 0.01) and COX-2 mRNA increased (P < 0.01). However, diabetic NOD mice had reduced COX mRNA response (P = 0.03). Vioxx administration influenced neither PGE(2), insulitis nor diabetes. We demonstrate an isoform switch in monocyte/macrophage COX mRNA expression following LPS, which is altered in diabetic NOD mice as in human diabetes. However, Vioxx failed to affect insulitis or diabetes. We conclude that monocyte responses are altered in diabetic NOD mice but COX-2 expression is unlikely to be critical to disease risk.

Cyclooxygenase in normal human tissues--is COX-1 really a constitutive isoform, and COX-2 an inducible isoform?

Cyclooxygenase (COX) is a key enzyme in prostanoid synthesis. It exists in two isoforms, COX-1 and COX-2. COX-1 is referred to as a ‘constitutive isoform’, and is considered to be expressed in most tissues under basal conditions. In contrast, COX-2 is referred to as an ‘inducible isoform’, which is believed to be undetectable in most normal tissues, but can be up-regulated during various conditions, many of them pathological. Even though the role of COX in homeostasis and disease in now well appreciated, controversial information is available concerning the distribution of COX isoforms in normal human tissues. There is mounting evidence that it is much more complex than generally believed. Our aim was therefore to analyse the expression and distribution of COX isoforms in normal human tissues, using immunohistochemistry, Western blotting and real-time RT-PCR. Autopsy samples from 20 healthy trauma victims and samples from 48 biopsy surgical specimens were included. COX-1 was found in blood vessels, interstitial cells, smooth muscle cells, platelets and mesothelial cells. In contrast, COX-2 was found predominantly in the parenchymal cells of many tissues, with few exceptions, for example the heart. Our results confirm the hypothesis that the distribution of COX isoforms in healthy tissues is much more complex than generally believed. This and previous studies indicate that both isoforms, not only COX-1, are present in many normal human tissues, and that both isoforms, not only COX-2, are up-regulated in various pathological conditions. We may have to revise the concept of ‘constitutive’ and ‘inducible’ COX isoforms.

Corticosteroids induce cyclooxygenase 1 expression in cardiomyocytes: role of glucocorticoid receptor and Sp3 transcription factor

Cyclooxygenase (COX) encodes a rate-limiting enzyme in the biosynthesis of prostanoids. Although COX-1 is constitutively expressed in many tissues, we found that glucocorticoids cause elevated expression of COX-1 gene in cardiomyocytes. Corticosterone (CT) at physiologically relevant doses (0.05-1 microm) induces transcriptional activation of COX-1 gene as shown by nuclear run-on and promoter reporter assays. An antagonist of glucocorticoid receptor (GR), mifepristone, prevented CT from inducing COX-1. COX-1 gene promoter deletion and mutation studies indicate a role of Sp transcription factors in CT-induced COX-1 gene. EMSAs or chromatin immunoprecipitation assays suggest that GR and Sp3 transcription factor bind to the promoter of COX-1 gene. Coimmunoprecipitation assays found an association of GR with Sp3. Silencing Sp3 protein with small interfering RNA suppressed CT-induced COX-1 promoter activation. Our data suggest that activated GR interacts with Sp3 transcription factor in binding to COX-1 promoter to enhance COX-1 gene expression in cardiomyocytes.

Inhibitors of GSK-3 prevent corticosterone from inducing COX-1 expression in cardiomyocytes

Our recent study has demonstrated that glucocorticoids (GCs) induce cyclooxygenase-1 (COX-1) gene expression in rat cardiomyocytes. While investigating the mechanism underlying corticosterone (CT) induced COX-1, we found that three structurally and mechanistically distinct GSK-3 inhibitors, LiCl, SB216763, and (2'Z,3'E)-6-Bromoindirubin-3'-oxime (BIO), inhibited COX-1 transcription and protein induction. A genetic approach of expressing wild type GSK-3beta increased COX-1 promoter activity, which was abolished by LiCl. LiCl increased inhibitory GSK-3alpha/beta phosphorylation at Ser21/Ser9, while BIO or SB216763 prevented stimulatory phosphorylation at Tyr279/Tyr216 of GSK-3alpha/beta. GSK inhibitors failed to block nuclear translocation of glucocorticoid receptor (GR) or activation of glucocorticoid response element (GRE) by CT treatment. While Sp3 transcription factor mediates CT induced COX-1 expression, GSK inhibitors did not change the level of Sp3 protein or binding of Sp3 transcription factor to COX-1 promoter. The observed effect of GSK-3 inhibitors appears to be unique to COX-1 since LiCl or BIO does not prevent CT from inducing COX-2 gene. We conclude that GSK-3 inhibitors block CT from inducing COX-1 gene expression via a mechanism beyond GR and Sp3 transcription factor.

Alveolar macrophage cytotoxic activity is inhibited by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a carcinogenic component of cigarette smoke

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a carcinogenic compound of cigarette smoke that generates electrophilic intermediates capable of damaging DNA. Recently, we have shown that NNK can modulate mediator production by alveolar macrophages (AM) and bronchial and alveolar epithelial cells, suggesting that cigarette smoke can alter lung immune response. Thus, we investigated the effect of NNK and cigarette smoke extract (CSE) on AM capacity to eliminate tumoral cells. Rat AM cell line, NR8383, was treated with NNK (500 microM) or CSE (3%) and stimulated with lipopolysaccharide (10 ng/ml). The release of cytotoxic mediators, tumor necrosis factor (TNF) and reactive oxygen species (ROS), was measured in cell-free supernatants using ELISA and superoxide anion production. TNF- and ROS-dependent cytotoxicity were studied using a (51)Chromium-release assay and WEHI-164 and P-815 cell lines. Treatment of AM with NNK and CSE for 18 h significantly inhibited AM TNF release. CSE exposure resulted in a significant increase of ROS production, whereas NNK did not. TNF-dependent cytotoxic activity of NR8383 and freshly isolated rat AM was significantly inhibited after treatment with NNK and CSE. Interestingly, although ROS production was stimulated by CSE and not affected by NNK, CSE inhibited AM ROS-dependent cytotoxicity. These results suggest that NNK may be one of the cigarette smoke components responsible for the reduction of pulmonary cytotoxicity. Thus, NNK may have a double pro-carcinogenic effect by contributing to DNA adduct formation and inhibiting AM cytotoxicity against tumoral cells.

The alpha7 nicotinic acetylcholine receptor as a pharmacological target for inflammation

The physiological regulation of the immune system encompasses comprehensive anti-inflammatory mechanisms that can be harnessed for the treatment of infectious and inflammatory disorders. Recent studies indicate that the vagal nerve, involved in control of heart rate, hormone secretion and gastrointestinal motility, is also an immunomodulator. In experimental models of inflammatory diseases, vagal nerve stimulation attenuates the production of proinflammatory cytokines and inhibits the inflammatory process. Acetylcholine, the principal neurotransmitter of the vagal nerve, controls immune cell functions via the alpha7 nicotinic acetylcholine receptor (alpha7nAChR). From a pharmacological perspective, nicotinic agonists are more efficient than acetylcholine at inhibiting the inflammatory signaling and the production of proinflammatory cytokines. This 'nicotinic anti-inflammatory pathway' may have clinical implications as treatment with nicotinic agonists can modulate the production of proinflammatory cytokines from immune cells. Nicotine has been tested in clinical trials as a treatment for inflammatory diseases such as ulcerative colitis, but the therapeutic potential of this mechanism is limited by the collateral toxicity of nicotine. Here, we review the recent advances that support the design of more specific receptor-selective nicotinic agonists that have anti-inflammatory effects while eluding its collateral toxicity.

Regulation of intracellular cyclooxygenase levels by gene transcription and protein degradation

Cyclooxygenases-1 and -2 (COX-1 and -2) catalyze the committed step in prostaglandin formation. Each isozyme subserves different biological functions. This is, at least in part, a consequence of differences in patterns of COX-1 and COX-2 expression. COX-1 is induced during development, and COX-1 mRNA and COX-1 protein are very stable. These latter properties can explain why COX-1 protein levels usually remain constant in those cells that express this isozyme. COX-2 is usually expressed inducibly in association with cell replication or differentiation. Both COX-2 mRNA and COX-2 protein have short half-lives relative to those of COX-1. Therefore, COX-2 protein is typically present for only a few hours after its synthesis. Here we review and develop the concepts that (a) COX-2 gene transcription can involve at least six different cis-acting promoter elements interacting with trans-acting factors generated by multiple, different signaling pathways, (b) the relative contribution of each cis-acting COX-2 promoter element depends on the cell type, the stimulus and the time following the stimulus and (c) a unique 27 amino acid instability element located just upstream of the C-terminus of COX-2 targets this isoform to the ER-associated degradation system and proteolysis by the cytosolic 26S proteasome.

Altered monocyte cyclooxygenase response to lipopolysaccharide in type 1 diabetes

Type 1 diabetes is caused by adaptive immune responses, but innate immunity is important because monocytes infiltrate islets. Activated monocytes express cyclooxygenase (COX)-2, promoting prostaglandin-E(2) (PGE(2)) secretion, whereas COX-1 expression is constitutive. We aimed to define monocyte COX expression in type 1 diabetes basally and after lipopolysaccharide (LPS) stimulation. Isolated CD14(+) monocytes were analyzed for COX mRNA and protein expression from identical twins (discordant for type 1 diabetes) and control subjects. Basal monocyte COX mRNA, protein expression, and PGE(2) secretion were normal in type 1 diabetic subjects. After LPS, twins and control subjects showed a COX mRNA isoform switch with decreased COX-1 mRNA (P < 0.01), increased COX-2 mRNA (P < 0.01), and increased COX-2 protein expression (P < 0.01). Compared with control subjects, both diabetic and nondiabetic twins showed greater LPS-induced downregulation of monocyte COX-1 mRNA (P = 0.02), reduced upregulation of COX-2 mRNA and protein (P < 0.03), and greater inhibition by the COX-2 inhibitor di-isopropylfluorophosphate (DFP) of monocyte PGE(2) (P < 0.007). We demonstrate an alteration in monocyte COX mRNA expression as well as monocyte COX-2 and PGE(2) production after LPS in type 1 diabetic patients and their nondiabetic twins. Because COX-2 response to LPS is proinflammatory, an inherited reduced response would predispose to chronic inflammatory diseases such as type 1 diabetes.

Association between Nonsteroidal Anti-inflammatory Drug Use and the Incidence of Lung Cancer in the Iowa Women's Health Study

BACKGROUND

Previous studies have suggested that use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) may be associated with reduced risk of lung cancer, but the data are inconsistent and are limited particularly with respect to the effects of aspirin, separate from other NSAIDs.

METHODS

The Iowa Women's Health Study is a prospective cohort of 41,836 Iowa women ages 55 to 69 years old at baseline in 1986. NSAID use was assessed in 1992. Over 10 years of follow-up, 403 incident cases of lung cancer were identified. The association of incident lung cancer with current use of aspirin or non-aspirin NSAIDs was analyzed after adjustment for lung cancer risk factors. Hazard ratios (HR) were estimated using multivariate COX proportional hazards regression.

RESULTS

There were 27,162 women in the analytic cohort. After controlling for age, education, alcohol intake, pack-years, smoking status, body mass index, and total fruit intake, the RR of women taking six or more aspirin weekly was 1.21 (95% confidence interval, 0.92-1.59). The HR was 1.23 for women taking six or more non-aspirin NSAIDs weekly (95% confidence interval, 0.92-1.65). There was no statistically significant trend by frequency of use for either aspirin (P(trend) = 0.22) or non-aspirin NSAIDs (P(trend) = 0.53). Analyses by histologic type and smoking status yielded similar null results. Information on dosage and duration of use were not available for this analysis.

CONCLUSION

These findings do not suggest that aspirin or other NSAIDs reduce risk of lung cancer in this cohort of postmenopausal women.

Formamidopyrimidine adducts are detected using the comet assay in human cells treated with reactive metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most lung-specific of the carcinogens present in tobacco smoke. Its bioactivation in cells leads to a small amount of methylation or pyridyloxobutylation DNA damage. Considering its great sensitivity, the comet assay seems a technique of choice to investigate NNK-related damage. Several strategies were used to impart some specificity to the assay: (1) using analogs that produce a limited variety of DNA lesions, as they mimic either the methylation or the pyridyloxobutylation pathway; (2) using cells with different bioactivation abilities; (3) using alkali conversion and/or enzymes specific for cleaving particular classes of damage; (4) using different lysis conditions to convert a specific class of DNA lesions into enzyme-sensitive lesions. We determined that several NNK-associated lesions can be detected with some specificity with the comet assay. For the methylation pathway, they are AP sites and the more frequent formamidopyrimidine (fapy) adducts. These fapy adducts correspond to N7-methylguanines generated in the cells that were ring-opened during the assay by the lysis solution at pH 10. For the pyridyloxobutylation pathway, alkylphosphotriesters and a roughly equal frequency of fapy sites were detected. By analogy to the methylation damage, these fapy adducts are thought to be the ring-opened form of N7-pyridyloxobutylguanines (N7-pobG). N7-pobG are unstable and this constitutes the first indirect demonstration of their formation in cells. But contrary to N7-m-fapy, the lysis time or pH did not influence the frequency of N7-pob-fapy adducts detected, suggesting that they already exist in the cells and are not related to the experimental conditions. These N7-pob-fapy have a strong mutagenic potential and we think that the comet assay, in spite of its limitations, is a good way to study them considering their low frequency and the inherent instability of the adduct from which they originate.

Activation of the nuclear factor kappaB pathway by astrocyte elevated gene-1: implications for tumor progression and metastasis

Astrocyte elevated gene-1 (AEG-1) was initially identified as an HIV-1- and tumor necrosis factor alpha (TNF-alpha)-inducible transcript in primary human fetal astrocytes by a rapid subtraction hybridization approach. Interestingly, AEG-1 expression is elevated in subsets of breast cancer, glioblastoma multiforme and melanoma cells and AEG-1 cooperates with Ha-ras to promote transformation of immortalized melanocytes. Activation of the transcription factor nuclear factor kappaB (NF-kappaB), a TNF-alpha downstream signaling component, is associated with several human illnesses, including cancer, and NF-kappaB controls the expression of multiple genes involved in tumor progression and metastasis. We now document that AEG-1 is a significant positive regulator of NF-kappaB. Enhanced expression of AEG-1 via a replication-incompetent adenovirus (Ad.AEG-1) in HeLa cells markedly increased binding of the transcriptional activator p50/p65 complex of NF-kappaB. The NF-kappaB activation induced by AEG-1 corresponded with degradation of IkappaBalpha and nuclear translocation of p65 that resulted in the induction of NF-kappaB downstream genes. Infection with an adenovirus expressing the mt32IkappaBalpha superrepressor (Ad.IkappaBalpha-mt32), which prevents p65 nuclear translocation, inhibited AEG-1-induced enhanced agar cloning efficiency and increased matrigel invasion of HeLa cells. We also document that TNF-alpha treatment resulted in nuclear translocation of both AEG-1 and p65 wherein these two proteins physically interacted, suggesting a potential mechanism by which AEG-1 could activate NF-kappaB. Our findings suggest that activation of NF-kappaB by AEG-1 could represent a key molecular mechanism by which AEG-1 promotes anchorage-independent growth and invasion, two central features of the neoplastic phenotype.

Oxidative stress in carcinogenesis. Correlation between lipid peroxidation and induction of preneoplastic lesions in rat hepatocarcinogenesis

Oxidative stress during carcinogen metabolism seems to participate in liver tumor production in the rat. N-diethylnitrosamine is an important carcinogen used in liver cancer animal models. This indirect alkylating agent produces DNA-ethyl adducts and oxidative stress. In contrast, N-ethyl-N-nitrosourea, a direct mutagen, which generates DNA-ethyl adducts, does not produce liver tumors in rat unless it is given under oxidative stress conditions such as partial hepatectomy or phenobarbital treatment. To gain insight into the relation between oxidative stress and hepatocarcinogenicity, the induction of preneoplastic liver lesions was compared among three different initiation protocols related to the initiation-promotion-resistant hepatocyte model. In addition, liver lipid peroxidation levels, determined as thiobarituric acid reactive substances were studied early during the initiation stage. Rats initiated with N-ethyl-N-nitrosourea, 25 days after treatment developed fewer and smaller gamma-glutamyl transpeptidase positive preneoplastic lesions than rats initiated with N-diethylnitrosamine. A pre-treatment with the antioxidant quercetin 1 h before N-diethylnitrosamine initiation, significantly prevented development of gamma-glutamyl transpeptidase-positive lesions. Increased lipid peroxidation levels were induced with N-diethylnitrosamine from 3 to 24 h after initiation, while N-ethyl-N-nitrosourea did not induce increments, and importantly, pre-treatment with quercetin decreased lipid peroxidation induced by N-diethylnitrosamine. These results show correlation between lipid peroxidation and hepatocarcinogenicity and support the important role of oxidative stress on liver carcinogenesis.

The modulating role of nuclear factor-kappaB in the action of alpha7-nicotinic acetylcholine receptor and cross-talk between 5-lipoxygenase and cyclooxygenase-2 in colon cancer growth induced by 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone

4-(N-Methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the tobacco-specific nitrosamine, induces lung cancer in all animal species tested and is thought to contribute significantly to the high lung cancer burden associated with smoking. However, there is no report whether NNK could promote colon cancer growth. To address this hypothesis and the possible signaling pathways involved, we used SW1116 colon cancer cell line to study these biological events in vitro. Results showed that NNK, after 5-h treatment, stimulated cell proliferation, enhanced alpha7-nicotinic acetylcholine receptor (alpha7-nAChR) mRNA levels and nuclear factor-kappaB (NF-kappaB) DNA binding activity, as well as 5-lipoxygenase and cyclooxygenase-2 protein expressions. alpha-Bungarotoxin, the specific alpha7-nAChR antagonist, inhibited these biological effects. However, 5-lipoxygenase inhibition had no effect on alpha7-nAChR mRNA expression, but significantly inhibited cell proliferation and activation of NF-kappaB and cyclooxygenase-2, whereas NF-kappaB-specific inhibitor caffeic acid phenethyl ester reduced both cell proliferation and cyclooxygenase expression induced by NNK without affecting alpha7-nAChR mRNA level and 5-lipoxygenase expression. Together, the present study demonstrated that NNK promoted colon cancer growth in vitro. NF-kappaB not only conveys the biological effect of alpha7-nAChR activation but is also involved in the cross-talk between 5-lipoxygenase and cyclooxygenase-2 in response to NNK in colon cancer cell development.

Synthesis, biological activity and molecular modeling studies of novel COX-1 inhibitors

Synthesis of new potential COX-1 and/or COX-2 inhibitors, derivatives of 1,1-di-(3-carboxyphenyl)ethane, their biological activity, docking results on COX-1 enzyme and absorption, distribution, metabolism, excretion (ADME) properties are presented. In addition to known interactions between ketoprofen and ibuprofen, leading NSAID agents and COX-1 active site, the possibility of formation of additional interactions is explored. Interactions with Ala527, and with one of the water molecules situated within the active site are identified. Molecular mechanics and DFT calculations for studied compounds have revealed free rotation around two central bonds (C1-C3' and C1-C3"), making them flexible, thus easier to enter and adjust to the active site. Further modifications of core structure have been undertaken to optimize biological activity and ADME properties. As a result, two of the compounds are indicated as novel COX-1 inhibitors.

Macrolide antibiotics inhibit prostaglandin E2 synthesis and mRNA expression of prostaglandin synthetic enzymes in human leukocytes

We investigated the action of macrolide antibiotics, which are considered to have anti-inflammatory activity, on lipopolysaccharide (LPS)-stimulated prostaglandin (PG) E2 synthesis and the expression of mRNAs for cytosolic phospholipase A2 (cPLA2), cyclooxygenase (COX)-1, and COX-2 in human leukocytes. The production of LPS-stimulated PGE2 was significantly increased in peripheral polymorphonuclear leukocytes (PMNLs) and in mononuclear leukocytes (MNLs). Amounts of mRNAs for COX-2 and cPLA2, but not for COX-1, were enhanced by LPS in PMNLs and MNLs. The LPS-enhanced PGE2 synthesis and the expression of cPLA2 and COX-2 mRNAs were inhibited by clarithromycin, azithromycin and dexamethasone in PMNLs and MNLs. The mRNA expression of COX-1 in PMNLs was decreased by clarithromycin and azithromycin. Macrolide antibiotics inhibited PGE2 synthesis in human leukocytes by suppressing cPLA2, COX-1, and COX-2 mRNA expression. These data indicate one mechanism of macrolide anti-inflammatory activity.

Biotransformation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in peripheral human lung microsomes

The contributions of different enzymes to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) biotransformation were assessed in human lung microsomes prepared from peripheral lung specimens obtained from seven subjects. Metabolite formation was expressed as a percentage of total recovered radioactivity from [5-3H]NNK and its metabolites per milligram of protein per minute. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol was the major metabolite formed in the presence of an NADPH-generating system, with production ranging from 0.5186 to 1.268%/mg of protein/min, and total NNK bioactivation (represented by the sum of the four alpha-carbon hydroxylation endpoint metabolites) ranged from 0.002100 to 0.005685% alpha-hydroxylation/mg of protein/min. Overall, production of bioactivation metabolites was greater than that of detoxication (i.e., N-oxidation) products. Based on total bioactivation, subjects could be classified as high or low NNK bioactivators. In the presence of an NADPH-generating system, microsomal formation of the endpoint metabolite 1-(3-pyridyl)-1-butanone-4-carboxylic acid (keto acid) was consistently higher than that of all other alpha-carbon hydroxylation endpoint metabolites. Contributions of cytochrome p450 (p450) enzymes to NNK oxidation were demonstrated by NADPH dependence, inhibition by carbon monoxide, and inhibition by the nonselective p450 inhibitors proadifen hydrochloride (SKF-525A) and 1-aminobenzotriazole (ABT), particularly in lung microsomes from high bioactivators. At 5.0 mM, ABT inhibited total NNK bioactivation by 54 to 100%, demonstrating the importance of ABT-sensitive enzyme(s) in human pulmonary NNK bioactivation. Contributions of CYP2A6 and/or CYP2A13, as well as CYP2B6, to NNK bioactivation were also suggested by selective chemical and antibody inhibition in lung microsomes from some subjects. It is likely that multiple p450 enzymes contribute to human pulmonary microsomal NNK bioactivation, and that these contributions vary between individuals.

Modulation of IL-12 p35 and p40 promoter activity by smokeless tobacco extract is associated with an effect upon activation of NF-kappaB but not IRF transcription factors

Interleukin (IL)-12 (p70), composed of p35 and p40 subunits, stimulates cellular immunity and inflammation. Stimulation of IL-12 production by smokeless tobacco extract (STE) could increase the chances of oral inflammatory disease. However, p40 forms homodimers and is part of IL-23 heterodimers. Expression of p35 and p40 in response to lipopolysaccharide (LPS) and interferon (IFN)-gamma requires activation of nuclear factor-kappa-B (NF-kappaB) and interferon regulatory factor (IRF) transcription factors. To determine the impact of STE on expression of p35 and p40, the activities of p35 and p40 promoter reporter plasmids in RAW264.7 cells stimulated with STE alone or in the presence of IFN-gamma and LPS were assessed. In addition, nuclear localizations of NF-kappaB p50, p65 and IRF-1, -2 and -8 in RAW264.7 cells treated with STE were evaluated. The results show that STE alone stimulates p40 and p35 promoter activity and enhances IFN-gamma-induced p40 and p35 promoter activity. In contrast, STE had no effect on LPS-induced p35 and p40 promoter activity and diminished IFN-gamma/LPS-induced p35 promoter activity. STE had little effect upon nuclear localization of IRFs, but it stimulated nuclear localization of both NF-kappaB p50 and p65. STE also stimulated IFN-gamma-induced activation of NF-kappaB p50 but reduced nuclear localization of IFN-gamma- and IFN-gamma/LPS-induced NF-kappaB p65. SN50, an inhibitor of NF-kappaB nuclear localization, significantly lowered STE-induced p35 and p40 promoter activity. These results suggest that STE stimulation of bioactive IL-12 production is correlated with its impact upon both p35 and p40 and can be attributed in part through an effect upon NF-kappaB p50 nuclear localization.

Environmental exposure and lung cancer among nonsmokers: an example of Taiwanese female lung cancer

Lung cancer is the leading cause of cancer death worldwide and in Taiwan. Cigarette smoking is considered to be the most important risk factor, since about 90% of lung cancer can be related to cigarette smoking. Despite the recent decrease of cigarette smoking, lung cancer is still the leading cause of cancer death in the United States. In Taiwan, only around 50% of lung cancer incidence could be associated with cigarette smoking, particularly less than 10% of Taiwanese women are smokers. Thus, the aetiology of lung cancer for nonsmokers remains unknown. DNA damages including bulky and oxidative damage may be related with mutation of tumor suppressor genes, such as p53 gene. The high DNA adduct levels in female may be associated with frequent exposure to indoor cooking oil fumes (COF) and outdoor heavy air pollution. Oxidative stress induced by COF was also discussed. Different p53 mutation spectra and mutation frequency between genders reflected that different environmental factors may be involved in nonsmoking male and female lung cancer development. Most importantly, our recent report has demonstrated that human papillomavirus (HPV) infection was associated with nonsmoking female lung cancer. Based on our studies with Taiwanese nonsmoking lung cancer as the model, the possible aetiological factors of lung cancer incidence in Taiwanese nonsmokers were elucidated.

Urinary bladder lesions induced by persistent chronic low-dose ionizing radiation

The incidence of urinary bladder cancer in the Ukraine increased from 26.2 to 43.3 per 100,000 population between 1986 and 2001 after the Chernobyl accident. The present study was conducted to evaluate the development of radiation-dependent lesions in the urinary bladders of people living in cesium 137 ((137)Cs) radio-contaminated areas of the Ukraine. Bladder urothelial biopsies from 159 male and 5 female patients were subjected to histological examination and immunohistochemical study of p38 mitogen-activated protein kinase (MAPK), as well as the p50 and p65 subunits of nuclear factor kappa B (NF-kappa B). A pattern of chronic proliferative atypical cystitis accompanied with large areas of sclerosis of connective tissue in the lamina propria was commonly observed in all cases. Interestingly, these lesions were associated with a dramatic increase in the incidences of dysplasia/carcinoma in situ, and, moreover, small urothelial carcinomas were incidentally detected. We defined the overall condition as "Chernobyl cystitis." Greatly elevated levels of p38, p65 and p50 expression in the urothelium were evident and the patients showed increased (137)Cs in urine. The data support conclusions from our previous studies of a critical role for increased oxidative stress in generation of urinary bladder urothelial lesions in individuals chronically exposed to low-dose (137)Cs radiation. Alterations in the p38 MAPK cascade and accumulation of NF-kappa B subunits could be crucial early molecular events in the pathogenesis of Chernobyl cystitis.

N-acetylcysteine ameliorates renal microcirculation: studies in rats

BACKGROUND

N-acetylcysteine (NAC) administration has been shown to ameliorate experimental acute renal failure induced by ischemia-reflow, and was found to prevent radiocontrast nephropathy in high-risk patients. While the protective effect of NAC has been primarily attributed to scavenging oxygen free radicals, improving renal microcirculation also may play a role in the prevention of acute renal failure.

METHODS

This study was designed to explore the effect of NAC on renal microcirculation. Blood pressure, total renal blood flow and selective regional cortical and outer medullary blood flow were continuously monitored in anesthetized Sprague Dawley rats with ultrasonic and laser-Doppler probes during the infusion of NAC (60 mg/kg).

RESULTS

In control intact rats blood pressure and renal microcirculation were unaffected by NAC. By contrast, following renal vasoconstriction induced by the radiocontrast agent iothalamate meglumine, NAC decreased total, cortical and medullary vascular resistance by 7 to 10% (P < 0.05). NAC also reduced renal vascular resistance by 16% when given during angiotensin II infusion (P < 0.05). Altered renal microcirculation, induced by the cyclooxygenase inhibitor indomethacin, by the nitric oxide synthase-inhibitor, Nomeganitro-l-arginine (L-NAME), or with their combination was partially restored by NAC. Nevertheless, NAC administration failed to attenuate renal function and morphology in a rat model of acute renal failure with selective outer medullary hypoxic injury, induced by indomethacin, L-NAME and iothalamate.

CONCLUSIONS

NAC ameliorates renal vasoconstriction, an effect that seems to be mediated by mechanisms other than prostaglandins and nitric oxide. The potential renoprotective outcome of NAC and the role of its vasodilating effect on the pre-constricted renal vasculature should be evaluated further.

Nuclear factor-kappa B and cancer: its role in prevention and therapy

Cancer is a hyperproliferative disorder in which invasion and angiogenesis lead to tumor metastasis. Several genes that mediate tumorigenesis and metastasis are regulated by a nuclear transcription factor, nuclear factor kappa B (NF-kappaB). A heterotrimeric complex consisting of p50, p65, and IkappaBalpha, NF-kappaB is present in its inactive state in the cytoplasm. When NF-kappaB is activated, IkappaBalpha is degraded and p50-p65 heterodimer is translocated to the nucleus, binds the DNA (at the promoter region), and activates gene. Research within the last few years has revealed that NF-kappaB is activated by carcinogens, tumor promoters, inflammatory cytokines, and by chemotherapeutic agents. The activation of NF-kappaB can suppress apoptosis, thus promoting chemoresistance and tumorigenesis. Interestingly, however, most chemopreventive agents appear to suppress the activation of the NF-kappaB through inhibition of NF-kappaB signaling pathway. These chemopreventive agents also sensitize the tumors to chemotherapeutic agents through abrogation of NF-kappaB activation. Overall, these observations suggest that NF-kappaB is an ideal target for chemoprevention and chemosensitization. This article reviews evidence supporting this hypothesis.

Cyclooxygenase isozymes and their gene structures and expression

The cyclooxygenase (COX, prostaglandin endoperoxide synthase) is a key enzyme in prostaglandin biosynthesis. Two isoforms of COX, COX-1 and COX-2, have been identified by molecular biological methods. The amino acid sequence homology between COX-1 and COX-2 is about 60% for the human enzymes. COX-1 is constitutively expressed in most tissues and cells in animal species. The COX-1 promoter region lacks a canonical TATA or CAAT box and is GC-rich. These features are consistent with those of a housekeeping gene. On the other hand, COX-2 is an inducible enzyme and is induced by various cytokines and mitogenic factors. The induction of COX-2 is suppressed by dexamethasone and PGJ2. There are many consensus cis-elements in the 5'-flanking region to regulate the expression of COX-2. Among them, a CRE, an NF-kappaB site, a NF-IL6 motif and an E-box, regulate transcription independently or synergistically. Most of the transcriptional signaling pathways require activation of the mitogen-activated protein kinase (MAPK) cascade. Moreover, MAPK signaling pathways are involved in regulating COX-2 gene expression at the post-transcriptional level.

Transcriptional regulation of cyclooxygenase-1 by histone deacetylase inhibitors in normal human astrocyte cells

While cyclooxygenase (COX)-2 is a highly inducible gene, COX-1 is widely known as a noninducible gene and is constitutively expressed in a variety of cell lines and human tissues. Recently, several reports have indicated that COX-1 is also regulated at the transcriptional level by various stimuli. We present evidence that histone deacetylase (HDAC) inhibitors induce COX-1 transcription and translation in normal human astrocyte (NHA) cells and glioma cell lines. HDAC inhibitors increased acetylated histone H4 protein expression in NHA cells. The levels of COX-1 mRNA and protein were maximal at 24 and 48 h, respectively, after treatment with the specific HDAC inhibitor, trichostatin A (TSA). In addition, TSA-treated NHA cells produced prostaglandin E(2) as determined by enzyme-linked immunosorbent assay after incubation with 10 microm exogenous arachidonic acid, indicating that the induced COX-1 is functionally active. In addition to NHA cells, this up-regulation of COX-1 after treatment with HDAC inhibitors was observed in 5 different glioma cell lines. The nucleotide sequence of the inducible COX-1 cDNA was confirmed identical to human COX-1 that was previously reported. HDAC inhibitors stimulated COX-1 promoter activity as measured by luciferase reporter assays, suggesting that the induction of COX-1 is regulated at the transcriptional level. Furthermore, mutation analysis of the COX-1 promoter suggests that TSA-responsive element exists in the proximal Sp1-binding site at +25 to +31. In conclusion, COX-1 is an inducible gene in glial-derived cells including immortalized cells, and appears to be transcriptionally regulated by a unique mechanism associated with histone acetylation.

Smokeless tobacco extract decreases IL-12 production from LPS-stimulated but increases IL-12 from IFN-gamma-stimulated macrophages

Modulation of IFN-gamma production from T cells by smokeless tobacco extract (STE) could be a factor in periodontal disease. The major inducer of IFN-gamma from T cells is bioactive IL-12 (p70), a heterodimeric protein composed of p35 and p40 subunits, while homodimeric IL-12 p40 antagonizes bioactive IL-12. Both p70 and p40 are produced by macrophages in response to lipopolysaccharide (LPS), IFN-gamma and/or CD40 ligation. To determine the impact of STE on IL-12 p40, p70 and IFN-gamma, splenic T cells were stimulated with anti-CD3 while splenic macrophages were stimulated with LPS in the presence or absence of STE. Production of IL-12 p40 and p70 from LPS-stimulated splenic macrophages and IL-12 p40, p70 and IFN-gamma from LPS/anti-CD3-stimulated T cells and macrophages was decreased by STE. To determine the impact of STE on macrophage IL-12 production alone, splenic or peritoneal macrophages were enriched and then stimulated. STE significantly diminished production of IL-12 p40 and p70 from LPS-stimulated peritoneal macrophages, LPS/IFN-gamma-stimulated peritoneal and splenic macrophages, but increased production of IL-12 p40 and p70 from IFN-gamma/CD40-stimulated splenic macrophages or IFN-gamma-stimulated peritoneal macrophages. None of the effects of STE on IL-12 was due to nicotine, rutin or chlorogenic acid. In contrast to STE, nicotine at 100 microg/ml significantly elevated production of IL-12 p40 and p70 from splenic macrophages stimulate by IFN-gamma/LPS. The results indicate that STE has a significant overall effect upon IL-12 production. It suppresses p40 and p70 production during responses to LPS or LPS/IFN-gamma but augments p40 and p70 production during responses to IFN-gamma without LPS. This affect could have a major impact on diseases associated with excessive production of IL-12.